Molded hollow articles of manufacture



Dec. 3, 1968 A. H. ROBERTS MOLDED HOLLOW ARTICLES OF MANUFACTURE 2Sheets-Sheet l Filed July 30, 1965 fl lf Il. Il Il Il Il Il It ,kann

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INVENTOR ARTHUR H. ROBERTS LAszLo AUE'R AGENT Dec. 3, 1968 A. I-I.ROBERTS 3,414,456

MOLDED HOLLOW ARTICLES OF MANUFACTURE Filed July 30, 1965 2 Sheets-Sheet2 FIG. l0.

Ia) BY SLuSI-I CASTING @L5M Ib) BY ROTATIONAL CASTING HEATING TO CAUSEGELATION (a) POURING OFF EXCESS FUSING SKIN PORTION STRIPPING Ii) ATROOM TEMPERATURE SKIN FROM OIE IIIIAT ELEVATED TEMPERATURE @iT-"i6-IIIAFTER PLACING SKIN IN SECOND DIE LATEX COMPOSITION BEHIND SKIN.IZIUSINC SKIN FOR MOLDING INNER LAYER DRYING INNER LAYER ELECTIVE?.PROVIDING FOR REINFORCING SPINE RECOVERING COMPOSITE ARTICLE INVENTORARTHUR H. ROBERTS BY I LASZLO AUER v AGENT United States Patent O y3,414,456 MOLDED HOLLOW ARTICLES OF MANUFACTURE Arthur H. Roberts,Brooklyn, N.Y. (12 Lynnwood Drive, Westbury, N.Y. 11590)Continuation-impart of application Ser. No. 22,002, Apr. 13, 1960. Thisapplication July 30, 1965, Ser. No. 475,989

19 Claims. (Cl. 161-7) ABSTRACT OF THE DISCLOSURE This inventioninvolves composite articles of manufacture having two components. Theouter layer component (skin) is a premolded pliable plastic illustratede.g. by vinyl chloride in a plasticized and polymerized state, ethylenein a polymerized state, a polyurethane elastomer and a flexiblepolyester resin. The inner layer component comprises a filler and theelastomer solids of a latex as a bonding agent. Illustrative to theelastomer are: natural rubber, copolymers of acrylic esters and acrylicacids, of vinyl chloride and acrylic esters, of vinyl chloride andacrylic acids. Clay, Whiting and silica illustrate the fillers. theinner layer is a highly pigmented composition and contains a substantialproportion of coarse particles of the fillers. An illustration of aprocess of manufacturing the articles of manufacture is to form the skinfrom plastisol by casting into a seamless die, removing the gelled andfused hollow outer layer from the die, casting the filler-containinglatex composition in the premolded skin, and drying the inner layeruntil the water is evaporated. The wall thickness of the outer layer isabout 151/2 to 250 mils. The articles of manufacture are impactresistant.

This is a continuation-in-part of my copending patent applications Ser.No. 22,002, led Apr. 13, 19601, for Method and Means for ManufacturingVarious Articles and Articles Produced Thereby, now abandoned and Ser.No. 455,764, filed May 14, 1965, for Impact Resistant Article and Methodof Manufacture.

This invention relates to novel, rigid, impact resistant manufacturedarticles. The articles are of varying sizes, may have more or lessintricate shapes and may have undercutsf Similar articles in the priorart were'made predominantly of ceramic or plaster materials. These priorart articles of manufacture have the disadvantages that they areextremely fragile, chip easily and have extremely low impact strength.To these disadvantages must also be added the disadvantage that they areuneconomical is that much hand finishing is required n the seam linescaused by the mold seams.

Alternatively, prior art has also utilized various casting processes formanufacturing seamless hollow articles out of plastisol and the like.The resulting product is quite attractive and can be decorated as easilyas plaster, and in fact more easily than ceramics. The plastisol articleso cast will not chip and is almost unbreakable. Also, if the die isseamless, a seamless product can be obtained. The use of plastisol,however, is very uneconomical since the material is expensive. Also,plastisol has defect called cold flow, which brings about a warpage atsub-tropical temperatures or in the vicinity of household radiators.Beside these defects, it has reduced impact strength at l'owtemperatures.

Therefore, prior art manufacturers of such articles as lamp bases havehad the choice of producing ceramic and plaster articles or the likewhich are inexpensive but very fragile, or producing plastisol articleswhich have good impact and chip resistance at normal temperatures, butwhich are uneconomical, have cold ow and poor im- Patented Dec. 3, 1968pact strength at low temperatures. The phenomenon of cold flow has alsobeen called heat distortion.

An object of this invention is to provide manufactured articles withimproved properties and without the disadvantages of the prior artarticles.

A further object is to provide small and large seamless hollow objectsof plastic with improved resistance to cold flow, chipping and breakage,and which is economically competitive with prior art products.

Other objects of this invention will become apparent from thedescription of this invention further below.

The articles of manufacture of this invention are rigid, arethree-dimensional and are hollow. They comprise two components: (l) anouter layer component, also called skin herein and (2) an inner layercomponent, also called flesh or rigidifier here below. In most of thecases varying cross sections of a single article show varyingmeasurements or shapes, indicating curved sidewalls and undercuts. Inother cases the cross sections may be identical, indicating box-shapedor cylindrical objects. As is will be seen, the fact that themanufactured articles of this invention are preferably hollow in theinitial steps of their manufacture, does not exclude that their cavitiesmay be lled to varying degrees with a reinforcing spine material.

The skin is preset in its shape by a molding operation. It is formedfrom a plastic material, which is preferably pliable and resilient.Depending on the plastic'material selected to form the skin, the moldingoperations may vary, in order to utilize the most advantageous methodfor the selected plastic. The outer surface of the skin readily receivescoloring materials for decorating the composite article. The inner wallsof the skin dene an internal cavity accessible through an opening in theskin. The inner layer component is in intimate contact with the innerwalls of the preset skin and is in supporting relationship to the outerlayer (skin). This inner layer acts as a rigidier and rigidly maintainsthe outer layer (skin) in its preset shape. The inner layer is formed bya latex bound composition and is described in detail further below. Thelatex composition is applied in a liquid state and solidies within thepreset skin. Thus, the skin acts as a mold in which to form therigidifying inner layer. Depending on the properties of the skin and thelatex composition, the setting of the latter may be performed while theskin is in a second mold or die. This second mold or die would usuallybe a split mold and is used to prevent deformation of the skin duringthe casting and setting of the latex bound composition forming the innerlayer. The latter acts as a structural rigid backing member. The use ofa second mold is superfluous in most cases.

The outer layer or skin component of the composite article ofmanufacture of this invention has a preferred wall thickness of about1%.; of an inch to about 1A of an inch. Expressed in thousandths of aninch, this corresponds to a range of from about 15.625 mils to about 250mils. The lower ligure may be rounded out to about 151/2 mils. The innerlayer or rigidifer iiesh component may have a wall thickness of equal tothe thickness of the skin, or even be as low as one half of thethickness of the skin. In -most cases the thickness of the inner layeris substantially greater than that of the skin. Comparative thicknessesvary with the skin and latex compound fonmulation utilized. For instancea comparatively more rigid skin may permit the application of a thinnerlayer of rigidifer than a more flexible type, while maintaining therigidier at the same composition. By varying the formulation of thelatex composition, a tougher or more rigid inner layer would permit theuse of a thinner layer than a less tough or less rigid inner layer,while maintaining the skin constant.

Inone of the embodiments of this invention the outer layer and innerlayer jointly form a second cavity and a reinforcing spine may beapplied as a third component in the entirety or in part of the secondcavity. Such a spine assists the rigidifying action of the inner layerand toughens the composite article of manufacture.

SKIN PORTION Plastisols illustrate an eminently suitable material toform the skin portion of the articles of manufacture of this invention.Plastisols are well described in the literature, as e.g. in ModernPlastics 26, 78 (April 1949) by Perrone and Neuwirth. They aredispersions of finely divided polyvinyl resin powders in liquid organicplasticizers. The resins contain predominantly polyvinyl chloride withor without some other polymerized monomer. They are polymerized to adegree where they have very low solubility at room temperature.Therefore, instead of dissolving them, the plastisols contain the resinsin a dispersed state; the dispersions are usually of creamy consistencyat room temperature and are always fluid to a certain'degree. A greatvariety of plasticizers can be used. Dioctyl phthalate is an example.Dioctyl adipate is another example, which frequently is used inadmixture with dioctyl phthalate. Polyester plasticizers are also Iwellknown. The plastisols usually contain a stabilizer and may containpigment, if so desired. For convenience and to achieve brevity, a fewpublications may be referred to, which all deal with plastisols, theirformulation and application methods: (a) Geon Resin 121 in PlastisolCompounding, Service Bulletin PR-4, Revised October 1958, B. F. GoodrichChemical Company, 24 pages. (b) The Vandenbilt News, vol. 26, No. 3,June 1960, R. T. Vanderbilt Company, Inc., page 12. (c) Modern PlasticsEncyclopedia Issue for 1961, published in September 1960, Vinyl Polymersand Copolymers, pages 129 to 132, Plastisol Molding, pages 765 to 771.(d) Modern Plastics Encyclopedia 1965, (issued 1964), Vinyl Polymers andCopolymers, page 271, Plastisol Molding, page 690.

When molding plastisols, the mater-ial is heated to a gellingtemperature and a gelled film or layer is formed which is very weak andcheesy, but which does not flow. Further heating is rqeuired to fuse thedeposit, causing the resin to dissolve in the plasticizer and form atough homogeneous resinous mass in which the powdered resin and liquidplasticizer have formed a single uniform phase. The fusion transformsthe cheesy deposit or film to a tough leather-like homogeneous layer orskin.

With regard to te-mperatures required, these are well known in the art.They vary from composition to composition. They vary with time. Thereare, further, three types of temperatures involved: 1) oven temperature,(2) mold (die) temperature and (3) temperature of the plastisol.Gelation temperature may be accomplished by heating the oven from 150 to600 F. and usually is between a plastisol temperature of 150 to 300 F.The necessary times vary with the temperature used. Fusion isaccomplished by heating the gelled layer in ovens from about 350 F. toabout 60 F. The achieved plastisol temperature for fusion shouldadvantageously range from about 350 to 450 F.

The most useful .molding methods for plastisol skins are illustrated by(a) slush molding, Ialso called slush casting and (b) rotationalmolding, also called rotational casting. The expression casting is usedbecause the plastisols are applied in fluid state and for this reasonthe operation has similarity to metallurgical casting. Seamless dies arepreferred for the intermediate products of this invention. They can bereadily utilized, even when complicated undercuts exist in the dies, asthe skins produced from the plastisols are flexible, elastic and have ashape memory, i.e., they recover from their stretched position, obtainedduring removal, t9 ih@ original molded shape.

When slush molding or slush casting is used, in the first step an excessof plastisol may be poured into the seamless die. As the plastisolreaches gelation temperature, the layer adjacent to the metal wall ofthe mold gels, i.e., solidifies. The thickness of the gelled wall isdetermined by the duration of time the mold is exposed to thetemperature of gelation. The excess plastisol is then removed by pouringoff the liquid portion. Heating is then continued to complete the fusionand the molded skin is then removed or stripped from the mold.

4There are two methods known in slush molding: (i) One Pour Method, and(ii) T wo Pour Method. Both are well known in the art and are applicableto make the skins of this invention from plastisols.

The rotational molding is another method of casting. The basic departurefrom the slush molding is that, instead of an excess of the liquidplastisol, a premeasured quantity of the fluid is used when charging thedie. This eliminates the need for removing any excess. The changed fluidplastisol is then distributed evenly in the die by rotating the same ona rotational molding machine. After the plastisol is properlydistributed, it is gelled by the application of heat and finally fused.The completed skin is then stripped and removed from the die.

Whereas the casting by slush molding or rotational molding is preferredto form the skins from plastisols, other methods known in the art mayalso be followed to achieve the same purpose.

Objects made of plastisols frequently display the defect known as coldflow. Cold flow may be defined as the warpage or flow of material caused'by its normal environmental temperature. Cold flow in plastics isanalogous to the warping of a wax candle in a hot climate, and when athermoplastic product is subjected to compression, tension or flexing,the cold flow characteristics become even more accentuated. When acondition of localized intensified heat, such as that to which lampbases are often subjected, is superimposed on a stressed article, coldflow warpa'ge becomes critical and often results in making further useof the article impossible. The application of a rigiditier in accordancewith the present invention counteracts the cold flow characteristics ofplastisol skins, or at least reduces them to commercially acceptablelimits.

Polyolens, such as polyethylene and polypropylene are other illustrativeexamples for the production of the skin portion of this invention.Polyethylene is made today of varying properties with the low pressureand high pressure polymerization processes. It is supplied with varyingdensities, molecular weights, flexibility and other characteristics. Thetypes of polyethylene most suitable for this invention are pliable,flexible and show some degree of elasticity. Polyethylene is preferredin this invention over polypropylene since it is more easily formed intopliable and flexible skins. Polyethylene copolymers, such asethylene-vinylacetate and ethylene-ethyl acrylate copolymers, olferimproved flexibility and resilience. They are rubber-like and similar toelastomeric plastics. For the production of skins from polyethylene andpolypropylene seamless dies are not satisfactory and two-piece dies arepreferred, using blow molding or other methods. Polyallomers belong tothis class of materials, as they are copolymers of ethylene andpropylene.

The skin portion of the articles of manufacture of this invention may beformed of other materials such as vulcanized natural rubber or syntheticrubber. The skins may be formed according to known procedures of rubbertechnology. One of the mehods useful in preparing skins from rubber isto use latex molding (latex casting) compounds, utilizing plaster ofParis molds. The Vanderbilt News, vol. 27, No. 4, December 1961, page72, deals with latex compounding which can be used to make skins forarticles according to the present invention.

Other suitable plastic materials, which can form the outer layer skinsof this invention are illustrated by methyl methacrylate polymer, ethylcellulose, polycarbonates, polyurethane elastomers, exible epoxycompounds, flexible polyesters, amongst others. Some illustrativeexamples are given below:

Example A.-Methyl methacrylate All percentages in this example and inthe specification are weight percentages. A mixture was prepared of62.5% methyl methacrylate monomer, 0.6% benzoyl peroxide, 2.1% plasticwhite color paste concentrate, compatible with methyl methacrylate,34.4% polyrnethylmethacrylate, DuPonts Lucite 30, 0.5%dimethyl-p-toluidine, totaling 100%. The skins are prepared by castinginto suitable molds. The composition of this example polymerizes at roomtemperature. Heating to 100-120 F. speeds up polymerizationconsiderably. Latex molds can be used. Plaster and clay molds can beused, if coated with gelatine, or cellulose acetate or sodium silicateor tin foil.- Casting was carried out in a latex mold in 3 subsequentcoats and yielded a molded skin with fair flexibility and good surface.Plasticizers may be incorporated, if desired. Harflex 340 of HarchemDivision, Wallace & Tiernan, Inc. is a suitable resinous-type, primary,nonmigrating, saturated polyester plasticizer, compatible with methylmethacrylate monomer. The color paste is used to stain the skin. Its useis optional.

Example B.-Polycarbonate Polycarbonates can be cast from organic solventsolutions. Polycarbonates dissolve, e.g. with ease in methylenechloride. A solution was prepared from Lexan No. 105 powder to form asolution of 83.3% polycarbonate in 16.7% methylene chloride, yielding100% of the solution. As an example, this solution can be slush cast inlatex molds, and air can be blown in to assist in Volatilizing thesolvent. The latex molds are standard in casting plaster of Parisobjects. The polycarbonate skin remains in the mold. It is very strong,flexible and durable, and can easily be stripped from the mold. Toreduce the effect of shrinkage, iillers may be incorporated. A ratio ofequal weights of tiller to polycarbonate is an illustrative example. Theresulting skin is still strong. Polycarbonate resins are marketed byGeneral Electric under the Trademark of Lexan. They can also be blowmolded and vacuum formed. l

Example C.-Flexible epoxy resin The proper composition has at leastthree ingredients. (1) a low molecular weight epoxy resin of theepichlorhydrinbisphenol A. condensation product type, like ShellChemicals Epon 828. (Epon is a registered trademark of Shell); (2) lowviscosity liquid aliphatic polyepoxides, like Epon Resin 871, whichimparts increased exibility to Epon resin compositions; and (3) a curingagent, illustrated by diethylenetriamine and Triethylenetriamine,respectively known as DTA and TETA. Other comparative items, known inthe trade, may be replaced for the commercial products mentioned.Fillers may be present as additional ingredients. A suitable additive toregulate viscosity is a submicroscopic pyrogenic silica prepared in ahot gaseous environment, marketed by Cabot Corporation under thetradename of Cab-O-Sil. A satisfactory composition to obtain skins is44.25% Epon Resin 828, 44.25% Epon Resin 871, 2.65% of Cab- O-Sil and8.85% diethylenetriamine, totaling 100%. This composition sets at roomtemperature in about 5 hours and at 80 C. it sets in 2 hours. Thecomposition may be varied according to principles known in the art.Skins can be prepared from latex molds or other elastomer molds. Theseare actually multi-pieced plaster of Paris molds externally reinforcingan entirely separate second flexible elastomer mold, having one openingfor pouring in the composition to be molded and set. The rubber forpouring in the composition to be molded and set. The rubber surface iscoated with a parting agent and the epoxy composition is slush cast intothe molds. The slit mold here described is used to mold skins showingundercuts. Other molds and molding methods can also be used, dependingon the article to be manufactured. Epoxy plasticizers include epoxycompounds of fatty oils and their acids. Epoxy novolac resins andcycloaliphatic epoxies are other illustrative members of this group.Polyamids and acid anhydrides may also be used as curing agents.

Example D.Flexible polyesters Polyester resins are usually made in twosteps. In the first step a condensation reaction is carried out betweena dibasic acid and a diol and this is then blended with a monomer.Maleic anhydride and fumarie acid are examples of the dibasic acids.Other unsaturated acids could also be used, like itaconic. Phthalicanhydride and isophthalic acid may be part components of the acids, tosecure desired modifications. The useful glycols form a long list knownin the art. Propylene glycol, ethylene glycol, diethylene glycol anddipropylene glycol are illustrative examples. Neopentyl glycol isanother example. Styrene is most frequenty used as the crosslinkingmonomer. Vinyl toluene is another example. Laminac is a registeredtrademark of American Cyanamid. Laminac Polyester Resin EPX-126-3 is aflexible polyester resin containing styrene monomer. A composition wasprepared from Laminac Polyester Resin EPXl263 92.6%, MEK peroxide 2.7%,Cobalt Naphthenate solution (6% Co) 0.27%, Laminac Additive #10,% 1.73%and Cab- O-Sil 2.7%, totaling MEK peroxide is methylethyl ketoneperoxide. Laminac Additive #10 is a petroleum wax composition dispersedin styrene, for ease of incorporation into polyesters. It improvessurface characteristics. The peroxide is the crosslinking agent and thecobalt assists the crosslinking. Flexible polyesters usually c011- tainlong chain acids or glycols. The gel time at room temperature is about10 minutes for this composition. The Cab-OiSil assists in regulating thethickness of the deposit if slush casting is used for molding. Two orthree coats can be slushed to obtain a desired skin thickness. The skinformation occurs at room temperature. More rigid polyesters can beblended with the flexible one used in this example, to vary properties.Latex molds and those utilized for epoxy resins, may be used withpolyesters.

Example E.-Isocyanate elastomers (urethane elastomers) Liquid urethanepolymers, such as DuPonts Adiprene L-100, can be transformed into tough,rubbery solids by reaction of the isocyanate group with polyamine orpolyol compounds. In addition, some materials which do not containactive hydrogens, such as the titanate esters, appear to catalyzecross-linking. Adiprene L-l00 can be cured with diamines, or moisture,or polyols, or by miscellaneous catalysts, such as lead or cobaltnaphthenate, potassium acetate and titanate esters. Tetrabutyltitanateis an example of the esters. One of the popular polyamines is MOCA,which is 4,4methylenebis-(2-chloroaniline). A formulation is illustratedby 100 parts of Adiprene L- 100 and 12.5 parts of MOCA, which gives aMOCA percent-equivalent of 95. Parts are by weight. Conditions were:Mixing temperature: 212 F., cure temperature: 212 F., curing time: 3hours. LD-420 is a different type of liquid urethane elastomer, whichyields high quality vulcanizates when cured with MOCA. A respectiveformulation is illustrated by 100 weight parts of LD-420 (DuPont) and8.8 weight parts of MOCA. This is mixed and cured the same way asAdiprene L-lOO, for the same length of time. It is improved byaftercuring 1 week at 75 F. at 60% relative humidity. In making a skinrotational molding is recommended both for Adiprene L-100 and forLD-420. A silicone mold release is advantageously used to assistseparation from the molds.

7 Example F.-Ethyl -cellulose Ethyl cellulose skins can be molded byvacuum forming and injection molding, amongst other methods. The sameapplies to cellulose acetate and cellulose acetobutyrate. Combination ofcasting and hot melt methods may also be used.

The present molded outer layers (skins) can be prepared by variousmolding processes. The selected process depends on the selected plasticmaterial and on the shape and size of the skin to be molded. Forillustrative purposes a few examples are given. Casting such as slushcasting or rotational casting: Plastisol, exible polyester, flexibleepoxy resins, methyl methacrylate, polycarbonates from solution, rubberfrom latex, etc. Injection molding or extrusion: plastisol,polycarbonates, ethyl cellulose, polyethylene, cellulose acetate,cellulose acetobutyrate, etc. Vacuum forming: polyethylene,polycarbonates, polyallomers, etc. Blow molding: polycarbonates,polyethylene, polyallomers, ethyl cellulose, cellulose acetate, etc. Hotmelt process: ethyl cellulose, plastisol or other plasticized polyvinylchloride composition, polyethylene, etc.

Whether a one-piece, two piece or multi-piece mold is required, dependson the selected skin material and, to some extent on the shape of themanufactured article. The molding process also influences the moldselection. Plastisol illustrates a skin forming material which permitsthe use of one-piece molds even if the skin has many undercuts in itsshape. Methyl methacrylate illustrates a material which requires atleast two-piece molds in most instances. Blow molding and vacuum formingare usually carried out in two-piece or multi-piece molds. One-piecemolds form seamless molded shapes. Two-piece molds cause, in most cases,some seam formation. It may be necessary to eliminate these seams.Therefore, seamless molding is of advantage.

The expression that the skin materials are flexible, pliable andresilient is meant in a relative manner in comparison with the innerlayer of the articles of manufacture, i.e. the esh portions which arerelatively rigid. The composite article itself is rigid and is resistantto breakage. The flesh portion rigidifies the flexible skins andimproves resistance to cold flow or heat distortion. The skin materialsprotect the rigidier flesh portion from fracture. This mutual improvingeffect between skin and flesh materials is unexpected and suprising andthe effect obtained could be described as synergistic.

From the skin materials discussed above, polyethylene andpolycarbonates, when blow molded, are used at a limited thickness. Inusing the various skin materials with the latex bonded filler innerlayers of this invention, the composite article manufactured showselimination of flexibility, improved resistance to impact and in manycases the tensile strength of the composite article shows improvementwhen compared separately to that of the skin or flesh material. Theinner layer also contributes to the weight of the composite article.These observations apply to skins made of plastisols, flexiblepolyesters, flexible epoxy resins, polyethylene, polypropylene,polyalomers, polyurethane elastomers, rubber, polycarbonate, ethylcellulose, methyl methacrylate, amongst others, The degree of the abovediscussed improvements may vary according to the selection of the skinforming material, its secondary compounding ingredients, thickness andshape of the skin, formulation of the flesh material and its thickness,amongst other factors.

In my parent applications, the specifically disclosed rigidifying eshportion was plaster of paris and asphalt. The latex bonded filler fleshportion of this invention shows great improvement over the use ofplaster of paris or asphalt. The ladvantages of the novel flesh portionover that disclosed in my parent applications could be summarized asfollows: (i) Only in rare cases an interior reinforcing spine isrequired for theflesh layer. On the other hand, plaster of paris andasphalt require such reinforcement in many cases. According to thisinvention the spine portion, if applied, is applied locally in selectedpositions only. (ii) It has greatly increased strength and resistance toimpact. (iii) In comparison with plaster of paris it requires much lesswater for application. The plaster of paris wet mix frequently containsabout 50% water when applied. As illustrated by the examples below, thelatex bonded filler composition requires much less water (I4-15% is aproper illustration). This provides for much faster drying of the innerlayer, faster prod-uction speed, and additionally, reduction inshrinkage during drying. (iv) In comparison with asphalt and thecolloidal combination of asphalt, rubber and polyethylene, theapplication temperature is of importance. The former materials requireelevated casting temperatures, whereas the latex bonded fillercompositions can be applied at room temperature by slush casting. Whenelevated temperatures are used for casting and the skin is thermoplasticin nature. as plastisol skins are, the skin requires a second supportingtwo-piece mold to prevent deformation at the required castingtemperatures of 200 to 250 F. In contrast thereto, the latex bondedcompositions can be slush cast directly into the molded skin and themolded skin may act as the solely required mold. Only in rare cases, ifthe skin is very soft, pliable and resilient, would a second mold be ofadvantage in holding the shape of the molded skin while a rigidifierlayer is placed behind the skin. The less pliable skins can be used asmolds themselves. This is a surprising fact when considering the sizeand weight of an object like a planter or a garden ornament or a birdbath. Some of these may have a height of 3 to 4 feet.

FLESH PORTION As described earlier, the esh portion of the products ofthis invention forms the inner layer, which in turn is snugly attachedto the outer layer and adheres thereto. One of the purposes of the innerlayer is to rigidity the outer layer skin portion. The rigidifyingaction is of particular importance, where the outer layer skin isflexible, according to a favored embodiment of this invention. A furtherobject of the inner layer is to provide body and possibly weight to thearticle of manufacture.

The inner layer is formed, according to this invention, from acomposition comprising (a) a binder component, (b) a filler component,(c) water and in most instances (d) auxiliary materials, required to setthe binder, or stabilize thecomposition or aid in dispersing thefillers.

(a) Binder component The binders herein used are latices either ofnatural or of synthetic origin. A latex, as the term is herein used, isa water dispersion of an elastomer. Latices are normally considered asbeing emulsions. A narrower interpretation of the term emulsiondescribes it as a dispersion in water of a water immiscible liquid.However, in most cases, the dispersed phase of latices `is a solid andtherefore the dispersion could be considered a suspension. It is assumedthat the rubber tree in fact emulsionpolymerizes the isoprene-typemonomer. Most synthetic latices are prepared by emulsion polymerizationof the monomer or monomer mixture. Other synthetic latices may representaqueous dispersions of elastomers, which have been obtained by otherpolymerization means, prior to emulsication. For the reason thatemulsion polymerization is the most frequent method of making syntheticlatices and the solidification of the monomer particles may beaccomplished at a later stage, the latices useful herein includeemulsions, where the dispersed binder is still in the liquid state.

The role of the latex in this invention is to bind the fillers to form asolid layer and preferably and additionally to provide adhesion of theinner layer to the inner surface of the outer layer skins. During thebinding process or formation of the inner layer, the water of the latexexapo-rates and the elastomer remains. While in latex form, the latexshould have good wetting power for the fillers used in the formulationof Vthe inner layer. Additional surface active agents can be added toincrease the wetting power or to stabilize the latex in question.

It is of advantage to use in the process of this invention a latex withas low a water content as is practical. In other words, a moreconcentrated latex is of advantage, providing it maintains its llerwetting properties. As the water has to evaporate and prolonged exposureto elevated temperatures is not desirable with many of the thermoplasticskins, high latex solids are of advantage. Latex concentration methodsare well known in the art. Centrifuging, careful evaporation of pa-rt ofthe water, creaming and electro-decantation are some of the methodsused. Electro-decantation is a combination of electrophoresis anddecantation. A practical level of latex solids may be illustrated by arange of from about 40% to about 65%. In some cases, lower or highersolid contents may also be used. Natural latex is available with a rangeof solids of from about 30% to about 75%.

The following is an illustrative list of latices useful in thepreparation of the flesh portion or inner layer of the products of thisinvention:

Natural rubber latex, like centrifuged natural Hevea latex;

Gutta Percha latex;

Balata Latex;

styrene-butadiene copolymer latices of varying monomer ratios;

Polyisoprene latex;

Neoprene latex;

Butadiene-acrylonitrile latices of varying monomer ratios;

Butyl rubber latex;

Polyvinyl chloride latices, plasticized either internally or byplasticizer emulsion addition;

Polyvinylidene chloride latex;

Vinyl chloride-acrylic copolymer latices;

Ethylene-propylene copolymer latex, emulsifed as a cement, afterpolymerization is completed;

Acrylic copolymer latices made of various monomer mixtures, amongstothers.

Examples of commercial latex products available and the names underwhich they are marketed, are as follows:

Centrifuged natural rubber latex: UNITEX (Stein Hall). Polyisoprenelatex: Shell Isoprene Latex 700 (Shell Chemical Company).Styrene-Butadiene latex: Pliolite 5352 (Goodyear) with a 30:70 styreneto butadiene ratio and Polyco 2422 (Borden Chemical Co.) with a 90:10styrene to butadiene ratio. Neoprene (polychloroprene) latices: NeopreneLatex 571 and Neoprene Latex 400 (DuPont). Butadiene-AcrylonitrileLatices: Non-reactive copolymers: Hycar 1551 and 1561 (highacrylonitrile), Hycar 1562 (medium acrylonitrile) (Hycar is a registeredtrademark of B. F. Goodrich Chemical Company). Reactive terpolymerscontaining in addition to butadiene and acrylonitrile a small quantityof an acrylic acid in a copolymerized state: Hycar 1571 (highacrylonitrile) and Hycar 1572 (medium acrylonitrile). Polyvinyl chlorideLatices: Geon 151. (Geon is a registered trademark of B. F. GoodrichChemical Company.) Polyvinyl chloride (P. V. C.) is not suitable as abinder as such and its latices have to be internally plasticized ormixed with a plasticizer emulsion or plasticizing elastomer latex. Latexplasticized poylvinyl chloride latex is illustrated by Geon 552 latex,which is an intermixture of a PVC latex and a latex of abutadiene-acrylonitrile copolymer. Geon 576 illustrates an internallyplasticized PVC latex, produced by copolymerizing vinyl chloride withmethyl acrylate. A plasticizer plasticized PVC latex is illustrated by alatex containing in its solid content 100 parts of a copolymer of 80parts of vinyl chloride and 20 parts of methyl acrylate and, in additionto said 100 parts, 35 parts of dioctyl phthalate in an emulsiiied state.Polyvinylidene chloride latices are rarely made as homopolymers.Examples of internally plasticized terpolymers are: (1) copolymer of 46parts of vinyl chloride, 27 parts of vinylidene chloride and 27 parts ofmethacrylic acid. (2) Copolymer of 46 parts of vinyl chloride, 27 partsof vinylidene chloride and 27 parts of methylhexyl acrylate. A product,which is an internally plasticized polyvinyl chloride and polyvinylidenechloride copolymer is Geon 450 x 167. Various other latices containingpolyvinyl chloride or polyvinylidene lchloride are Geon 351, Geon 652,Dow Latex 700 (Dow Chemical), Pliolite 300 (Goodyear), Polyvinyl acetatehomopolymer is illustrated 'by Polyco 117-H (Borden Chemical Company).

The expression acrylic polymer is considered for the purposes of thisinvention as a generic term which includes acrylic copolymers, i.e.polymers made of more than one acrylic monomer. An acrylic monomer is anacrylic type acid, its derivatives and substitution products of the acidand its derivatives. The term derivative includes esters and nitriles.

The term an acrylic type acid is a polymerizable alpha-beta unsaturatedmonovinylidene carboxylic acid, such as acrylic acid, methacrylic acid,ethacrylic acid, alpha-chloroacrylic acid, cinnamic acid, atropic acid,crotonic acid. Preferred are acrylic and methacrylic acids. Halogensubstituted acrylic acids are also advantageous.

The elastomers of this invention comprising an acrylic polymer areinsoluble in water.

Examples of nitrile derivatives are: acrylonitrile andmethacrylonitrile.

Examples of ester-forming alcohols are the following: Alkyl alcohols,such as methyl, ethyl, n-propyl, iso-propyl, 2-methyl pentanol,3,5,5-trimethylhexyl, tertiary butyl, octadecenyl alcohol. Substitutedalkyl alcohols, such as chloroethyl, chlorobutyl, 2rnethoxyethyl,2-butoxyethyl, 2-nitro-2-methyl propyl, oxoalcohol of an isobutylenedimer, alkoxyethyl; Alicyclic alcohols, such as cyclohexanol andmethylcyclohexanol; Aromatic alcohols, like phenols and araliphaticalcohols, like benzyl alcohol; Heterocyclic alcohols, like furfuryl andtetrahydrofurfuryl alcohol. Preferred alcohols have 1 to 18 C atoms intheir aliphatic chain and the most commonly used ones have no more than8 C atoms.

Acrylic acid homopolymers do not belong to this class, as they are watersoluble. Acrylic esters as homopolymers, or copolymerized alone, can notbe crosslinked with ease. Acrylic nitriles as homopolymers yieldproducts that are too tough. Binary copolymers of acrylic acids withacrylic nitriles and binary copolymers of acrylic acids with acrylicesters can be crosslinked. One of the good copolymers is at leastternary and contains acrylic esters, nitriles and acids copolymerized.The acrylic acids in copolymers run between 2% to 15% of the totalcopolymer. Nitriles do not exceed, if used, 40% of the total, and 15 to30% represents a satisfactory range. Acrylic ester content of thecopolymers may go as high as to 98%, if nitriles are absent. Wherenitriles are present, the ester content may range from 40 to 80%.Elastomer content can be varied by intermxing the respective individuallatices.

Prepolymerized elastomers may be emulsied in the presence or absence oforganic water-immscible solvents, to form latex-type binders. RoyaleneP-3520 is an emulsied cement, made by U.S. Rubber, from prepolymerizedethylene-propylene copolymer. Neoprene cements can also be emulsied.

So called carboxy-modified copolymers can be crosslinked many times bythe action of heat alone or by the addition of vulcanizing agents withor without application of heat. Hycar 1570 x 20 is a carboxy-modifiedbutadiene/acrylonitrile latex suitable for coagulant dipping. It hashigh tensile strength, outstanding abrasion resistance and good oil andsolvent resistance. lts acrylonitrile content is characterized asmedium-high. Its stress-strain properties can be varied from thosecharacteristic of a rubber elastomer to those typical of a polyurethaneelastomer. It can be vulcanized by certain metal oxides or salts alone.Zinc oxide or sodium aluminate may be used as sole vulcanizing agent. Astandard sulfur/zinc oxide/ accelerator system may be used forvulcanization also. Zinc oxide levels and pH changes can vary itsproperties, greatly. Calcium nitrate in methanol solution is arecommended coagulant.

A carboxy-modified butadiene-styrene polymer is illustrated by Good-rite2570 x 5. (Good-rite is a registered trademark of B. F. GoodrichChemical Co.) It has the ability to cure by the application of heatalone. Heat crosslinking can be catalyzed by the addition of oxalic acidor ammonium chloride, permitting lower curing temperatures. Of courseregular cures with conventional curing systems are also useful. A thirdcuring system is zinc oxide or sodium aluminate. These act upon thecarboxylic portion of the polymer. Sodium aluminate cures in 3 days atroom temperature. Zinc oxide performs similarly in the presence orabsence of sulfur.

A useful class of reactive acrylic copolymers is illustrated by Hycar2671, Hycar 2600 x 92 and Hycar 2600 x 113. Hycar 2671 is anionic andyields, upon air-drying at room temperature, properties which arevaluable for many applications. For curing, it requires temperatures offrom about 300 to about 325 F. Acid salts, like diammonium acidphosphate and ammonium chloride, lower the curing temperature.Crosslinking agents can be utilized, like glyoxal, butylene glycol,triazine resins melamine,acrylic resins, etc. It has good resistance todiscoloration. Hycar 2600 x 92 is a modification of Hycar 2671 withimproved resistance to discoloration by light and heat, otherwise havingsimilar hardness or softness properties. It has greater modules and lesselongation than 2671 after 3 days room-temperature drying. Oxalic acidcatalyzes its cures and lowers curing temperature. Zinc oxide is afavorable additive. Hycar 2600 x 113 is heat reactive and much softerthan 2671 or 2600 x 92. A cure cycle of 3-7 minutes at 300 F. issuitable. Oxalic acid or ammonium chloride catalyze the crosslinking andlower the required temperature. It shows remarkable stability tomultivalent ion salts, alcohols, solvents, etc. It can be cured at 212F. in 3 minutes to acceptable strength. Hycar 2600 x 112 is a similarcopolymer with film forming heat reactivity at as low as 150 F. It hasincreased hardness compared t 2671 and 2600 X 92. Hycar 2600 x 112 doesnot form films at room temperature and requires elevated temperaturesfor performance.

It will be realized that physical strength of the flesh portion willdepend on the particular latex binder applied, presence or absence ofcrosslinking or curing and the filler combination used.

It is possible to vulcanize natural rubber particles in dispersed state,i.e. in latex form. Upon drying, such latex immediately forms strongvulcanized films. Such a latex was marketed under the trade name ofVultex with about Z50-33% N.V. and in concentrated form under the tradename of Revultex with about 60-65% N.V. Such vulcanized or crosslinkedelastomer latices are also useful in this invention.

(b) Filler component The fillers of the flesh portion may be varied.Pigments, like titanium dioxide, lithopone, zinc sulfide, zinc oxide andothers used in emulsion paint formulations may be used. Extenderpigments and coarse fillers may also be used. Various types of clays orKaolins, calcium carbonate (natural or precipitated), such as Whiting,and coarser materials, like iiint (SiO-2) can be utilized. A 60 meshsilica illustrates the coarser materials. Talc and magnesium silicate,barium sulfate, colored pigments, like iron oxides, ochres, etc. may beused. Addition of small quantities of fibrous materials to the fillersmay help to strengthen the inner layer portion of this invention. Asbestos fibers, short staple fiberglass may be mentioned as examples. Theillustrative examples here below use a com- 12 bination of Whiting,McNamee Clay and fiint (silica) in a satisfactory proportion.

Other examples of fillers are: shell flour, carbon black, diatomaceousearth, aluminum hydroxide, hydrated alumina, bauxite powder, magnesiumcarbonate, dolomite powder (calcium-magnesium carbonate), mica, etc. Forthe coarse particle size component vitreous rock of igneous origin maybe used. Portland cement forms with latices interesting compositions,while it binds Part of its water content. With proper care Portlandcement may be incorporated as part of the fillers,

Coarse fillers have greatly reduced surface area, compared with fineparticle size fillers. Therefore, a coarse filler can be loaded into alatex mix in comparatively high proportion, without requiring additionalbinder content. The coarse fillers help to reduce the danger of crackingduring drying and assist in decreasing shrinkage to a considerableextent.

When using clays as part of the filler, the soft clays, like McNameeclay, are more advantageous, than the hard clays, like Dixie clay.

To calculate surface area of pigments and fillers the following equationis used:

Total surfaces are=6W/Sd wherein Wzweight, S=specific gravity andd=average diameter of particles in centimeters. This discussion relatesto the pigments and fillers of Example 1. The Yorkshire Whiting has asurface area of 10,000 square centimeters per gram. The McNamee Clay hasa specific gravity of 2.5 and an average diameter of particles of 1.2microns. These figures yield a surface area for the clay of 2,000 squarecentimeters per gram. The 60 mesh silica has an average particlediameter of 0.025 cm and a specific gravity of 2.4. These figures yielda surface area for the silica of square centimeters per gram. Table 1shows the analysis of the figures, as obtained from Example 1, below.

TABLE 1 Percent Percent Surface Percent Filler in dry in filler in sq.cm. in surface weight niix in 1 gr. of arcaoflgr.

filler of filler McNamee C1ay 9.75 10. 7G 215.2 6.18 YorkshireWhiting.-. 29.14 32.18 3,218. 0 92. 34 60 mesh Silica 51. 68 57.0651.7 1. 48

Total 90. 57 100. 00 3, 484. 9 100. 00

Dry

(c) Auxiliary material component The various latices have varyingdegrees of mechanical stability. Many of them require additionalstabilization to secure resistance to shear in mixing operations andstability in storage in the presence of the fillers used. Latexstabilizers are one type of auxiliary material. Igepals are examples oflatex stabilizers. They are alkylphenoxypoly (ethyleneoxy)ethanols. Someare nonyl phenol condensation products with ethylene oxide. IgepalCA-630 is an example of latex stabilizers. Igepal is a registeredtrademark of Antara Division of General Aniline and Film Corp.

Surface active agents may be added for pigment and filler dispersingpurposes also. They might simultaneously act as latex stabilizers.Darvan 7 is an example of such 13 agents and is a sodium salt of apolyelectrolyte marketed by R. T. Vanderbilt Co.

Vulcanizing agents and/or vulcanizing activators are exemplied by sulfurand zinc oxide. They are incorporated preferably as water dispersionsinto the latex compositions. Various crosslinking agents could beclassified at this point and are mentioned elsewhere in thisspecification, designating where they may be advantageously used. Theylower crosslinking temperature or accelerate the required duration.

Vulcanization accelerators are another group of possible auxiliarymaterials. A number of accelerators are mentioned, together with tradenames of R. T. Vanderbilt Co., under which they are marketed, asfollows: Dithiocarbamate type ultra accelerators: zincdibutyldithiocarbamate (Butyl Zimate), aqueous solution of sodiumdibutyldithiocarbamate (Butyl Namate) aqueous solution of potassiumdibutyldithiocarbamate (Butyl Kamate), activated dithiocarbamate (ButylEight or Setsit 51). Thiuram type ultra accelerators: Tetraethylthiuramdisulfide (Ethyl Tuads) and dipentamethylene thiuram tetrasulfide(Sulfads).

Ultra accelerators were selected for illustration, as low temperature orroom temperature cures are of advantage in this invention.

Butyl Zimate yields fast cures with natural rubber, styrene-butadienerubber (SBR), neoprene and nitrile latices. Ethyl Tuads and Butyl Namateor Kamate accelerate the cure of neoprene latices. Setsit-l curesnatural latex at room temperature and accelerates the cure of otherelastomers. The thiuram ultra acclerators contain available sulfur andmay be used in sulfur-free formulations, i.e. where all the vulcanizingsulfur is derived from the accelerator. Ethyl Tuads contain in cubes10.8% and in rods 9.8% of available sulfur. Sulfads contain in powderform 25% and in rod form 22.5% available sulfur. Sulfads alone, withoutadditional sulfur, is a vulcanizing agent for natural rubber,butadienestyrene and butyl rubbers. It is a primary accelerator forbutyl rubber and a secondary accelerator for most elastomers.

The auxiliary materials also include antioxidants. Examples with tradenames, refer to products of R. T. Vanderbilt Co.: Agerite Spar is astyrenated phenol type antioxidant. Agerite Superlite is a mixture ofpolybutylated Bisphenol A.

Another group of auxiliary agents of latex compositions is representedby softeners, such as plasticizers. These are incorporated as solutionsor emulsions. They also may be added per se to emulsify into the latexcomposition during addition. Still another group is represented bythickeners, such as salts of polycarboxylic acids, casein,methylcellulose and carboxymethylcellulose salts. The proper thickenerdiffers for the various types of latices.

PROPORTIONS AND RELATIONSHIPS PERTAIN- ING TO THE FLESH PORTION Withregard to proportions, it should be understood that the requirementsvary greatly depending -on the outside or skin layer used, the type ofend product manufactured, the latex utilized and the fillers selected.Therefore the proportions and relationships mentioned herein areillustrations of the invention to assist in its understanding and arenot intended as limitations thereof.

With the latter understanding, it is stated, that the thickness of theinner layer or flesh portion ranges from about mils to about 500 mils inmost cases and in the plurality of practical applications its thicknessis at least that of the outer layer or skin portion of the manufacturedproduct.

For the discussion in this paragraph, the latex solids are considered asthe elastomer content of the latex. This is the enitre non-volatileportion of the latex. The latex solids may have a varying relationshipto the fillers. A

practical relationship is illustrated by a range from about 200 weightparts to about 2000 weight parts of filler for each weight parts of theelastomer binder. In the illustrative examples below, the range isbetween 300 weight parts to about 1000 weight parts of filler per 100weight parts of elastomer. The particle size of the fillers, i.e. theirtotal surface area and the comparative iexibility and toughness of theused elastomer may require variations in the proper ratios. Generallyspeaking, the water containing tiesh-forming mixes are highly loadedlatex compositions, that is, they have comparatively high fillercontent.

As mentioned above, the coarse portion of the fillers has a distinctrole in the process. It is advantageous that in the total fillercomponent of the esh-forming composition the coarse particle sizefillers represent more than 50% of the total weight of the tillers. Apractical useful range could be given as from about 40% to about 70% ofthe filler component. This range is based on the assumption that thecoarse ller particle size is about 60 mesh. The proper proportions wouldchange, should the relationship of the particle sizes (diameters) andsurface areas of the coarses to the lines vary.

As the water content of the flesh-forming latex composition has to beevaporated during the manufacturing process, it is advantageous to haveas low a Water content as possible, or practical. The water content maybe illustrated by a range of from about 10% to about 20% of the totalweight of the composition. In some cases the water content may go up ashigh as 25% or more.

PREPARATION OF THE LATEX COMPOSITION AND PREPARATION OF THE INNER LAYERIn one embodiment of this invention the latex composition is prepared in4 steps. In the rst step in Vat A dispersing agents, water and the finerparticle size fillers are mixed and theiillers dispersed. Some of theauxiliary components may be incorporated here. Examples of ingredientsin the first step are McNamee clay (kaolin) and Yorkshire Whiting asfillers, water and Darvan 7 in 25% aqueous solution, as a dispersingagent. If sulfur is used for vulcanization, its water dispersion can beadded here and the same applies to zinc oxide, where it is used as thevulcanizing agent or activator. Where alkaline stabilization isrequired, potassium hydroxide solution or ammonia can be added here too.

In the second step the latex portion is weighed out into Vat B. Alsolatex stabilizers and additional dispersing agents may be added to Vat Bas we ll as vulcanization accelerators and antioxidants. Potassiumhydroxide or ammonia may be added here tooif such is advantageous forstabilization. Additives, which are soluble in water, are added as watersolutions. Water-insoluble additives are preferably added as waterdispensions.

In step three Vats A and B are mixed with each other. In a subsequentfourth step the coarse filler is added and mixed into the composition tocomplete its formulation. Suitable agitation is provided for each of thefour steps. These four steps are given here for illustrative purposes.Variations are possible without necessarily changing the end results.Thickeners may be added, where desired or required, during any one ofthe four steps. A sixty mesh silica is an example of a coarse fillerportion.

In production control, a standard sized panel of the skin formingmaterial is dipped into the latex composition and the pick-up isestablished on a square inch basis. When the flow of this type ofcomposition stops during draining, the balance is in a non-owingsomewhat gelled condition and canl easily be weighed. If the pick-up istoo high, the composition is thinned with water. If it is too low,thickeners are added. A suitable thickner, if required, is Polyco 2896of the Borden Chemical Co., which is a sodium polyacrylate. It is usedin water solution. In many instances the dried first coat will pick up11/2 to 21/2 times its own weight, to form the second coat;

If a third dipping is made, the third coat is usually equal to thesecond coat in weight.

The dipping corresponds to the coat which remains in a premolded skinduring the first, second and third slush-casting. The pickup per coat ofslush casting is similar to that acquired by dipping of the test pannel.As an illustration: when a molded skin portion weighs 2 pounds, thefirst coat of slush casting provides about 1 pound of flesh portion fromthe latex composition. The second slush casting provides a pick-up of 2pounds and the third one provides another 2 pounds, bringing the totalweight to 7 pounds. Triple slush casting of the flesh portion is usuallythe maximum required for proper thickness and/or rigidication. Slushcasting may be carried out by hand pouring of the latex composition intothe preformed skins. Rotation casting may be used also.

A suitable means for accelerating the drying of latex compositions toform the ilesh portion is to blow air into the interior of the moldedarticles. Depending on air circulation, humidity, etc., the drying timefor each coat may take 5 to 15 hours or more. Application of heat,vacuum or acceleration of exhaust, amongst others, may furtheraccelerate the drying. In selecting temperatures one has to consider thepossible thermoplastic nature of the skins used. If curing, crosslinkingor vulcanization is contemplated, it can be carried out after the waterhas been evaporated from the inner layer of the manufactured products.Vulcanization at 250 F for 15 to 20 minutes is given as an example fornatural rubber bonded inner layers, providing primary and secondaryaccelerators and activators are present in proper combination.

At this point, it may be mentioned that when the latex bonded innerlayer is in position behind the premolded skins and the inner layer isreasonably dry, the composite molded article in most cases can beexposed to vulcanization temperatures of about 250 F. without anydeformation of the plastisol or other thermoplastic skins. In theabsence of the inner layer and the simultaneous absence of a protectivesecond mold, the premolded plastisol skins, for instance, may deform atas low a temperature as `120 F. The latex bonded inner layer holds thepremolded skins in shape and permits vulcanization or curing at elevatedtemperatures without the application of protective second molds.

After the application of the inner layer is completed the manufacturedproducts are ready for decoration. If trimming the products is planned,this is advantageously carried out prior to decoration.

In some instances, like in the case of bird bath displays for gardensand planters for owers and plants, the inner layer is exposed to liquidwater for prolonged periods. In such cases it is advantageous toadditionally waterproof the inner layer. An example for waterproofing isthe application, by slush casting, of a 2 component ilexible epoxycoating. The latter may be loaded with llers to the extent of -50% ofthe coating material solids.

Another problem may be encountered where large compressive forces areplaced on narrow members of the manufactured products, like on neckportions of lamp bases. The tightening of sockets into such narrow necksmay require the application of strong forces. A solution of such aproblem is illustrated by rst placing the tubing, through which theelectrical wiring is led to the socket into the lamp base and thenfilling the narrow portion or neck portion of the lamp base with a rigidpolyurethane foam forming composition. This composition solidies whereit is placed and causes a local additional reinforcement.

Changing the composition forming the inner layer with regard to llersmay decrease the adhesion to the premolded skins, like those made fromplastisols. In such cases it may be advantageous to apply adhesivelayers between the outer layer and inner layer of the manufacturedproducts. Elastomer adhesives may be applied from solution, frequentlyalso called rubber cements. I have found 16 that the clay ller incombination with the latex binder brings about good adhesion in theformulation of the illustrative examples below.

ILLUSTRATIVE EXAMPLES OF THE INNER LAYER FORMING COMPOSITIONS Theexamples given below are for the purpose of illustration and are notintended to limit this invention. Example 1 describes a natural rubberlatex bonded inner layer forming composition, which will be the modelfor the comparative examples below.

Example 1.-Hevea latex The following ingredients and proportions wereused in Example 1:

Dry Wet content in Dry weight, wet weight, weight, percent percentpercent Weight Part A:

Water 8. G4 10% Aqueous KOH solution 0. 53 0.05 0. O6 60% Aqueous zincoxide dispersion 0. 26 O. 16 0. 19 25% Aqueous Darvan I solution. 0.770.19 0.22 68% Aqueous sulfur dispersion..- 0. 11 0. 07 0. 08 McNameeClay (Kaolin) 8. 32 8. 32 9.75 Yorkshire Whiting 24.87 24. 87 29.14

Subtotal for Part A 43.50 33. 66 39. 44

Part B:

Natural centrifuged latex,

62.5% N.V 1l, 75 7. 34 8. 60 10%7 Aqueous KOH solution 0.36 0. 04 0.0525% Aqueous Darvan 7 solution. 0. 07 0. 02 l). 02 65% Aqueous dispersionof Agerite Spar 0.11 0.07 0. 08 Setsit 51 accelerator 100% 0.11 0.11 0.13

Subtotal for Part B 12.40 7. 58 8.88

Part C: Mex Parts A+B 55. 90 41.24 48.32 Part D: Silica 60 mesh 44.1044.10 51. 68

Total 100.00 85. 34 100.00

The latex used in the example was Unitex, centrifuged natural Hevealatex of Stein-Hall. The dispersions of zinc oxide and sulfur are fromR. T. Vanderbilt Co., marketed for latex compounding. Darvan 7 andSetsit 51 are also supplied by Vanderbilt as used. The water content ofthis composition is about 14.66%, of which 9.84% is in Part A and 4.82%in Part B, both based on total weight 0f the entire composition. Mixingprocedure was as outlined further above. Based on latex solids theapproximate percentage of sulfur is 1%, of zinc oxide about 2% and ofthe accelerator Setsit 5l, about 11/2%. The anti-oxidant is about 1% ofthe rubber solids. In this example the approximate weight proportions ona wet basis are: Part A 43.5%, Part B 12.4%, silica 44.1%, totalingExample 2.-Isoprene elastomer latex In this example the ller proportionsused were similar to those used in Example 1. The elastomer was derivedfrom Shell Isoprene Latex 700, which had 65.5% nonvolatile content(N.V.). The elastomer content of the dry composition was 8.57% and ofthe wet composition 11.2%. The KOH content was similar to that ofExample 1: the same applies to Darvan 7. However, both were -added intheir entirety to Part A. Based on 100 elastomer solids about 1.6% zincoxide dry, 11/2% Agerite Superlite, 1% Methyl Zimate, 2% Sulfads, all ona dry basis, were used, applied from water solutions or Vdispersions.The Agerite Superlite had 65%, the Sulfads 50%, the Methyl Zimate had55% N.V. content, as used, to supply the given dry percentages. A smallamount of thickener could be used in this case, as the viscosity wasslightly lower than the optimum for slush casting. The resulting innerlayer was softer than that made of Example 1 and being more iiexible,may permit additional filler ncorporation, to increase rigidity. Thecomposition was free of added sulfur and the sulfur of vulcanization wasderived from the Sulfads. The water content of this example Example3.-Butadiene-acrylonitrile latex In this example Hycar 1570 x 20 latexwas used, which is a carboxy-modied butadiene/acrylonitrile latex having43.4% N.V. The fillers were the same and in similar proportions as usedin Example 1. The elastomer dry content in the composition was 8.68%.The additives on a dry basis per 100 elastomer parts were about: 3% zincoxide, 1% sulfur, 1% Agerite Superlite, 1% Setsit 51, and 0.9% EthylZimate. All additives were added from water dispersions or solutions,except Setsit 51, which incorporates with ease as 100% solids. No KOHwas used in this example. The dispersing agent was Darvan 7, all of itpresent in Part A. The water content of this composition was about18.3%. A fraction of Borden Chemical Cos. Polyco 2896 thickener was usedin this composition as an additive, as the mix was originally orslightly low viscosity. This composition should be slush cast incomparatively thin layers, to avoid cracking during drying. Strength wasobtained at room temperature. When placed in an oven for l hour at 250F. additional hardness developed. Addit-ion of dioctyl phthalateplasticizer in the proportion of 10-20%, based on elastomer solids,improves exibility and toughness of the inner layer obtained. Theplasticizer is advantageously pre-emulsiied.

Example 4.-Neoprene latex The composition of the filler components andthe-ir proportions in the dry inner layer were the same as in Example l.The latex used was Neoprene Latex 571, having 50% N.V., supplied byDuPont. In 100 parts of dry inner layer the elastomer content was 8.44%.KOH was present in Part A and in 100 parts of dry inner layer the dryKOH content was 0.11%. Darvan 7 was the dispersing agent and was part ofPart A as in Example 1. On a dry bas-is, the following additives werepresent for every 100 weight parts of elastomer solids: about parts ofzinc oxide, 2 parts of Neozone D Special, 3 parts of Aquarex SMO, 1 partof Aquarex WAQ, 1 part of Tepidone and 0 5 part of Thiuram E. Theingredients were all added in aqueous dispersion or solution. Zinc oxidewas incorporated in Part A and was the vulcanizing agent. The remaininglisted additives were incorporated -in Part B. Aquarex SMO is a surfaceconditioner and contains the sodium salt of sulfated methyl oleate;Aquarex WAQ is sodium lauryl sulfate; Tepidone is a 47% solution ofsodium-dibutyldithiocarbamate in water; Thiuram E is tetraethylthiuramdisuliide; Neozone D is phenyl-betanaphthylamine. All the additivesincorporated in Part B are marketed by DuPont. The Water content was17.4%. The preparation of this composition required care, as silica isnot easy to disperse in neoprene latices. The latter require highalkalinity. Additional stabilization may be achieved with ammoniumcaseinate, containing dimethylamine. The resulting inner layer, afterdrying, was usable, but less attractive in its properties than the oneobtained from Example 1.

Example tyrene-butadiene latex The kcomposition of the ller componentsand their proportions in the dry inner layer were, for practicalpurposes the same as in Example 1. The latex used was Pliolite 5352 ofGoodyear, having 69% N.V. The monomer ratio of this latex is 30% styreneto 70% butadiene. A small quantity of KOH was used both in Part A and B.The additives on a dry basis, based on 100 parts of elastomer solids,were: about 2% zinc oxide, 1% sulfur, 1% Agerite Spar, 11/2 Setsit 51.Darvan 7 was present both in Part A and B as a dispersing agent. The pHwas kept between 8.5 and 10. The water content of the composition wasabout 13.34%. The composition deposited heavy layers in casting andgelled rapidly. It took longer to dry than the natural latex compositionof Example 1. It was aftercured at 250 F. for 1/2 hour. The cure atelevated temperature made the inner layer harder. The natural rubberlatex formulation of Example 1 showed somewhat better adhesion to aplastisol formed skin and showed better strength properties than theproduct of this example, as formulated. An increase of the letex contentof this composition seems to be indicated as advantageous,

Example 6.-Ethy1ene-propylene copolymer latex In this example, Part Bcontained Royalene P-3520 latex of U.S. Rubber Co. This is made from anethylenepropylene copolymer elastomer converted first to a rubber cementand then emulsied. The latex as supplied, has 45% N.V. content. In thecomposition of this example no additives were added for the purposes ofvulcanization, crosslinking or preservation from aging. Some additivesare believed to be present in the original rubber cement. The fillercontent and the proportion of the 3 fillers was essentially similar tothat applied in Example 1. Darvan 7 was used in Part A for dispersingpurposes. In the dry content of the composition the elastomer N.V.portion was 8.76% and the KOH content was about 0.11%. The KOH wasincorporated into Part A. The water content of the composition formingthe inner layer in this example was 18.45%. The procedure forpreparation of the composition was similar to that applied in Example 1.The pH was regulated to be between 10 and 11. Care had to be exercisedin the step of adding the 60 Mesh Silica, to avoid coagulation. Theresulting inner layer was usable, but showed less strength than theproduct of Example 1.

The Royalene type copolymers perform favorably with pigment and lillermixtures containing carbon black, calcined clays and Hi Sil. Sulfurcures Royalene, preferably in the presence of zinc oxide. The supplierrecommends the use of dithiocarbamate type accelerators in the presenceof stearic acid.

Example 7. -Carboxyl modified butadienestyrene latex The latex'- used inthis example was Good-rite 2570 x 5 from Goodrich, which is a carboxylicmodified butadienestyrene polymer. It has the ability to cure by heatalone, or by the addition of zinc oxide or sodium aluminate, amongstothers. It is shipped with about 42% N.V. In Part B of this example thelatex was applied alone to yield 8.73% elastomer content in the drycontent of the composition. The fillers were about the same as inExample 1 and the incorporation method was the same. Darvan 7 was usedin Part A as a dispersing agent. Zinc oxide dispersion was also presentin Part A to yield about 5% ZnO per 100 parts of elastomer solids. Thecomposition mixed well and showed slightly lower viscosity than desired.This was corrected by adding a fraction of a percent of BordensThickener 2896, which is a sodium polyacrylate. For prestabilizing thislatex 2% Igepal type stabilizer may be added to the wet latex, likeIgepal `Co-630. The resultant inner layer was hard and somewhat brittle.A 5 minute cure at 300 F. was applied. This latex type may beadvantageously intermixed with natural rubber latex. The water contentin this example was about 19.2%. This composition worked well at roomtemperature, when it was air blown dry and when applied in thinnerlayers. The formulation used Zinc oxide alone as the crosslinking agentand had no sulfur present. This type of latex is film forming and curesat room temperature to strong lilms in 3 days time, when it containsparts of elastomer solids: 5 parts of ZnO, 2 parts of sulfur, 2 parts ofSetsit 5 accelerator and 2 parts of carbon black. The carbon black isoptional.

Example 8. Acrylic type latex In the composition of this example thelatex used was Hycar 2600 x 113, having 51.4% N.V. content. The

properties of this latex have ben described further above. It is areactive acrylic latex, having carboxylic modification in the polymer.Its lm cures upon heating and its cure can be catalyzed by oxalic acidor ammonium chloride. Its iilm is soft and exible and can be used asplasticizer for other latices. In this example the latex was used as thesole constituent of Part B, yielding 8.84% elastomer, based on the totaldry content of the composition. The llers were the same, having the sameproportions and incorporated as described in Example 1. Darvan 7 was thedispersing agent in Part A. No other additives Were present, except thefillers. The ingredients mixed With case and the composition could beapplied with ease. Room temperature drying was applied. Heating the dryinner layer for 3-7 minutes to Z50-300 F. further improved toughness.

This example was repeated With Hycar 2600 x 92, which is similar innature to Hycar 2600 x 113, but is tougher. The N.V. content of thelatex Was 50.7%. The ingredients and composition of the dry content ofthe latex composition was the same as above. This alternative of theexample yielded an inner layer deposit which Was more rigid at roomtemperature drying. Heat cure is advantageous.

The Water content of the composition with Hycar 2600 x 113 Was about16.3%. The inner layer formed by this composition was excellent in everyrespect. As shown, no crosslinking agent was applied, but such could beutilized.

Example 9. -Vinyl chloride-acrylic copolymer latex In this example, Geon450 x 23 latex was used, having 53.7% N.V. This type of latex is filmforming at room temperature and does not require curing or crosslinkingfor ultimate performance. It has high pigment binding power and derivesits toughness from the vinyl cornponent and the heat and light stabilityfrom the acrylic component. Geon 450 x 23 is the softest of thecorresponding series and has greatest filler loadability. It was used asthe sole ingredient in Part B of the composition, to yield 8.84%elastomer content in the total dry content. The fillers were the same,their proportions the same and their incorporation method the same as inExample l. Darvan 7 was the dispersing agent applied in Part A. No otheradditives Were present as auxiliary agents. The preparation was madewith ease and the viscosity, while a little on the low side, Was usableWithout addition of thickener. It coated the molded plastisol skins Welland upon room temperature drying gave an excellent qualityinner layer.The dry ratio of Darvan to elastomer solids was 1.14 to 100 parts. Thiswas a smaller ratio than in the other examples. 'The Water content ofthe composition was about 15.7%.

Example 10. -Intermixes of high styrene SBR latex with hevea latex Inthis example intermixes were prepared of a High Styrene SBR latex andthe Hevea latex used in Example 1. As the High Styrene SBR latex, Polyco2422 of the Borden Co. Was used, which has a 90.10 styrene to butadieneratio and had about 50% N.V. content. Three preparations were made,marked respectively (a), (b) and (c), as follows: In 10a the totalelastomer solids were kept about the same as in Example 1 and theelastomer solids of the intermix had about High Styrene SBR latex solidsand 80% Hevea latex solids (natural rubber). In 10b the elastomer solidsof the intermix had about equal parts of High Styrene SBR latex solidsand Hevea latex solids and the total elastomer solids in the dry contentof the composition have been increased with about 84%. This wasaccomplished by roughly doubling the elastomer solids on the iillercontent. In practice additional SBR latex was added to the compositionof Example 1, yielding additional latex solids equal to that previouslypresent. In 10-c the elastomer solids of the intermix had about twoparts of natural rubber latex solids to each single part of the HighStyrene SBR latex solids and the latex solids per filler content weretripled. This means that to the composition of Example 1 enoughadditional Hevea latex was added to double the natural rubber solids andadditional High Styrene SBR latex was also added to yield as much of itselastomer solids, as natural rubber latex elastomer solids were presentin the composition of Example 1. The resulting compositions have beensluch cast into molded skins and compared With each other both after airdrying and low temperature curing. The inner layer obtained from Example10-a was more brittle, than the one obtained from Example 1. It wasstill useful. The inner layer of lO-b was stronger and less brittle thanthe one of Example 1. The inner layer of lO-c was stronger and showedexceptional flexibility when compared with the one obtained fromExample 1. In Table 2 following, some pertinent data are given in acomparative manner.

TAB LE 2 Example 1 10a 10-b 10-C Total Solids (N. V.), percent .34 84.65 80.86 78 .45 Total Water, percent 14 .66 15 .35 19 .14 21.55 Partspresent, based on parts of elastomer solids, of following:

.04 58 .86 37 .78 Whiting 32B .10 169.83 112 .94 Silica 60 Mesh- 582 .39300 .75 199 .23

Total Filler 1, 053 .14 1, 020 .53 529 .44 349 .95

Total Fines* 452.21 438 .14 228 .69 .72

The Total Fines equal the sum of the clay and Whiting.

Some of the ingredients are based on the filler content, others on thevulcanizable elastomer solids, accounting -for the specific iigureslisted. The High Styrene SBR latex solids are not considered to bevulcanizable, because of the high styrene content. In 10-c and in 10-bthe natural latex solids derived from the addition of Part B of Example1 and therefore a seeming irregularity exists on 100 elastomer vbasisfor some of the ingredients.

The total ller content, based on total elastomer solids ranges fromabout 3.5-times in Example 10-e to about 10.5 times in Example l forformulation purposes the line fillers, which are pigment size particles,are in a different category from the coarses. The nes cause increase inviscosity of the liquid composition as the loading is increased. At thetime the coarses (Part D) are incorporated, the viscosity of the liquidcomposition hardly shows any change. The nes pass through a 200 or 300mesh screen -and may be even finer. The coarses pass through a coarsemesh screen, illustrated by a 60 mesh screen. The surface area of thecoarses is much smaller per Weight unit than that of the fines. It ispossible to produce satisfactory inner layer composition with a smallerthan 31/2 times ratio of tiller to elastomer solids, providing the finespredominate or are used exclusively. The role of the coarses in thelatex compositions forming the inner layer of this invention is topromote drying speed, reduce danger of mud-cracking and lower the costof the inner layer. Their presence improves the possibility of producingcomparatively thicker layers per slush casting step. If the silica isincreased in the formutation of Example 1 beyond the present proportion,the rigidiication would be increased, `but the impact resistance wouldbe decreased. If the clay is increased and the Whiting correspondinglydecreased, the rigidity increases. The Whiting improves resistance toshrinkage, as clays have high shrinkage. When the Whiting is increasedand the clay is decreased, the resulting inner layer is less rigid andis softer. In a proper formulation careful consideration should be givento the warpage.

The method of preparation of the illustrative examples of thecompositions forming the inner layers can be varied. It was foundconvenient to follow the 4 step process outlined above. e.g., byincorporating the superaccelerators and sulfur and zinc oxides indifferent portions, storage stability of the individual portions can beachieved. However, if the storage stability is of no importance, or ifthe composition does not vulcanize or destabilize on standing, eg. whenthe composition is used up fast, or where stable non-vulcanizing latexis used single full batches can be prepared in one step.

As mentioned further above, the proper viscosity of a latex compositionsuitable to form the inner layer can be established by dipping a pannelof the skin into the composition. A satisfactory viscosity isillustrated by a pickup of about 1.5 to about 1.6 grams per square inch.This type of composition will yield, -by slush casting, a pickup ofabout 225 grams or 1/2 pound per square foot of skin area in the firstcoat. The second `and third coats deposit about double of that obtainedin the first coat. In a practical example, where 1 square Afoot ofmolded skin weighed 1.3 lbs., the first coat caused a pickup of 0.5 lb..and the second and third coat each deposited 1.0 additional lb.,totaling a weight of 3.8 lbs. per square foot for the linished article.Of course, the shape of the rarticle and exact formulation of the latexcomposition may alter the results. The weights given .are for wetpickup. In this instance the wet inner layers weight is about twice theweight of the molded skin outer layer.

In the drawings:

FIG. 1 is a vertical cross-sectional view of a single piece moldutilized in the present invention showing an undercut. 11 is the metalmold.

FIG. 2 is a vertical cross-sectional view of the mold of FIG. 1 in whicha skin 12 was molded.

FIG. 3 is a vertical cross-sectional view of the mold of FIG. 1,illustrating the removal of the plastisol skin 12 from the mold. Theskin is in a somewhat collapsed state, but regains its original shapeafter removal and cooling.

FIG. 4 is a vertical cross-sectional view of a composite article ofmanufacture. The skin 12 of this article was molded in the mold of FIG.l and the inner layer 13 is snugly attached to the said skin. The innerlayer 13 is also called rigidilier or flesh portion in the descriptionfurther above.

FIG. 5 is a vertical cross-sectional view of a composite article ofmanufacture having a cylindrical shape. This article has no undercuts.12 is the outer layer or skin portion and 13 is the inner layer or fleshportion. 18 is the extension to be removed by trimming. This extensionfacilitates the manufacturing of the article.

FIG. 6 is a vertical cross-sectional view of a lamp. 12 is the skin; 13is the latex bonded inner layer; 14 is a rigid urethane foam layer; 15is a metal tube to lead the electrical wiring to the socket, and 16 is aseparate ybase for the lamp. The rigid polyurethane foam 14 acts as asecondary reinforcing support, applied discontinuously, in the localposition where the reinforcing action is required. The lamp base 16 maybe of metal or wood or a plastic material. Instead of metal tubing, thetubing of 15 may be of other suitable material, like a plastic. Therigid polyurethane foam acts as a reinforcing spine.

FIG. 7 is a vertical cross-sectional view of an ornamental base tosupport heavy loads. It can be utilized indoors or in gardens. 12 is theouter layer; 13 is the latex bonded inner layer; 14 is a rigidpolyurethane foam layer, and 17 is a paper tube to act as an additionalreinforcing spine. The upper end of the tube is sealed.

FIG. 8 is a vertical crosssectional view of a hollow article ofmanufacture. 12 is the outer layer or skin; 13 is the inner layer orflesh portion and 19 is a reinforcing spine of metal utilized tostrengthen the narrow neck portion of the manufactured article.

FIG. 9 is a vertical cross-sectional view of an arm rest piece forfurniture. 12 is the skin or outside layer; 13 is the rigidifying innerlayer; 15 is a metal tube acting as a reinforcing spine and 20 is afilled polyester layer acting in a similar manner to the rigidpolyurethane foam in FIG. 6 and FIG. 7.

It may be stated that the spine layers 14 in FIG. 7 and 20 in FIG. 9 aredistributed on a comparatively larger area of the cavity in view of theunusual stresses to which the respective composite articles are exposedduring their use.

FIG. 10 is a schematic ow sheet.

The composite articles of manufacture of this invention comprise latexbonded fillers as the inner layer. The properties of this inner layerexclude, in most cases, the need for reinforcing spines. In some rarecases, such spines are of advantage in reinforcing local areas of thecomposite articles. FIGURES 6 and 8 illustrate such cases. The spineportion may be cast or placed -behind the latex bonded inner layers.Metal may be applied by casting. The lower the melting point of themetal the less problems arise during casting. In many instances, metalsWith melting points of around 700 F. may be successfully cast intocavities formed jointly by the skin and inner layer. This can beexplained by the cooling action of the skin-layer system on the castthin metal layer required.

An illustrative flow diagram of one of the suitable processes of thisinvention is shown in FIG. 10, as follows:

Step 1: Casting fluid plastisol in a seamless die;

Alternative (a): by slush casting, Alternative (b): by rotationalcasting (molding);

Step 2: Heating the plastisol to a sufficient temperature and for asuicient time to cause gelation of the plastisol adjacent to the die;

In Alternative (a) pouring olf the excess liquid plastisol;

Step 3: Heating the die and gelled plastisol to a temperature and for atime sufficient to fuse the gelled plasti- Asol to a tough skin;

Step 4: Stripping the skin from the die:

Alternative (i) at room temperature, Alternative (ii) at suitableelevated temperature;

Step 5: Slush casting a filler containing liquid latex compositionbehind the skin to form an inner layer;

Alternative (1): after first placing the skin into a twopiece seconddie, having the same shape as the first die.

Alternative (2): using the molded skin itself to form the inner layerbehind it;

Step 6: Drying the composition forming the inner layer;

Step 7: (Elective alternative): Providing for a reinforcing spine in thejointly formed cavity of the skin and inner layer materials;

Step 8: Recovering the composite article of manufacture so formed Inrotational molding no excess of plastisol has to be poured olf. Gelationtemperatures may vary, depending on the composition of the plastisol,duration of heat and whether the temperature of the oven or of the dieor of the plastisol are taken. Gelation can be achieved satisfactorilyat plastisol temperatures of to 300 F. or at oven temperatures of 150 to600 F., providing the duration of heating is properly adjusted. Fusioncan be achieved ybetween 350 and 650 F., depending on other factors,such as duration. Normally, plastisol temperatures of 350 to 450 F.yield satisfactory results.

Examples of the spine are metal and rigid polyurethane foam. When spinesare used, they are mostly used for 23 local reinforcement in selectedportions of the composite articles of manufacture.

Slush casting can be carried out with the so called One Pour Method orthe Two Pour Method. In the slush casting of the inner layer frequentlythe casting-drying cycle is repeated more than twice.

If elevated temperatures are used in stripping the plastisol skin fromthe die, a temperature of 140 F. illustrates a suitable temperature.

The drying of the cast filler-containing liquid latex composition, toform the dry inner layer, can be carried out at room temperature or atsomewhat elevated temperatures. A stream of air led into the individualcavities of the hollow articles promotes drying.

The two-piece die used in Step 5, alternative (l), may conveniently be amulti-piece die comprising more than two pieces.

The above described flow sheet is to be appropriately modified ifanother skin forming plastic is used than plastisol, providing theselected plastic is not suitable for slush casting or rotationalmolding. The applicable molding methods for each plastic are well knownin the art and are illustrated in the description further above.

An advantageous top limit in the inner layer is for instance, 1500 partsof filler for each 100 parts of elastomer solids. In such cases thecoarses exceed 50% of the total weight of the iillers.

Among the advantages of the present invention are that the resultingarticles of manufacture have a high impact and chip resistance; are freeof heat distortion in practical applications; are inexpensive tomanufacture and may be readily mass-produced by the process of theinstant invention.

It is apparent that the described examples are capable of manyvariations and modifications within the scope of the instant invention.All such variations and modifications are to be included within thescope of this invention.

What I claim:

1. A rigid hollow composite article of manufacture comprising an outerlayer component and an inner layer component, said outer layer componentbeing a premolded plastic layer having a wall thickness of from about15.5 mils to about 250 mils, the plastic being pliable and the innerlayer component being a rigid composition comprising a filler bonded bythe elastomer solids of a latex said inner layer being in intimatecontact with the inner walls of the outer layer and engaged with theentire extent thereof, and wherein said inner layer component containsat least about 200 weight parts of filler for each 100 weight parts ofelastomer solids.

2. The composite article of claim 1, wherein parallel cross-sections ofthe article taken at different positions show varying measurements andshapes, indicating curved sidewalls and the existence of undercuts.

3. yThe composite article of claim 1, wherein the outer layer and innerlayer components jointly form a cavity in which a reinforcing spine isplaced at least in a single local position requiring additionalreinforcement.

4. The composte article of claim 1, wherein the wall thickness of theinner layer is atleast that of the outer layer and not more than 500mils.

5. The composite article of claim 1, wherein the outer layer comprises aplasticized polyvinyl chloride.

6. The composite article of claim 1, wherein the outer layer comprises acopolymer of vinyl chloride in a plasticized state.

7. The composite article of claim 1, wherein the outer layer comprisesethylene in a polymerized state.

8. The composite article of claim 1, wherein the outer layer comprises apolyurethane elastomer.

9. The composite article of claim 1, wherein the outer layer comprises aflexible polyester resin.

10. The composite article of claim 1, wherein the elastomer solids ofthe inner layer component comprise natural rubber latex solids.

11. The composite article of claim 1, wherein the elastomer solids ofthe inner layer component comprise the latex solids of a copolymercomprising an acrylic ester and an acrylic acid.

12. The composite article of claim 1, wherein the elastomer solids ofthe inner layer component comprise vinyl chloride and an acrylic acid.

13. The composite article of claim 1, wherein the elastomer solids ofthe inner layer component comprise vinyl chloride and an acrylic ester.

14. The composite article of claim 1, wherein the fillers in the innerlayer component range from about 200 weight parts to about 2000 weightparts for each 100 weight parts of elastomer solids.

15. The composite article of claim 1, wherein the lillers in the innerlayer component range from about 300 weight parts to about 1000 weightparts for each 100 weight parts of elastomer solids.

16. The composite article of claim 1, wherein the coarse particle sizefillers in the filler portion of the inner layer component range fromabout 40% to about of the said iiller portion, the percents being byweight.

17. The composite article of claim 1, wherein the coarse particle sizefillers in the liller portion of the inner layer component exceed 50% ofthe total weight of the fillers and pass through a 60 mesh screen,whereas the fine particle size llers pass through a 200 mesh screen.

18. The composite article of claim 1, wherein the filler portion of theinner layer component consists of about l0 to 11% of clay, about 30 to33% of Whiting and of about 56 to 60% of a 60 mesh silica, allpercentages being by weight.

19. A rigid hollow composite article of manufacture comprising an outerlayer component and an inner layer component, said outer layer componentbeing a premolded plastic layer having a wall thickness of from aboutl5l/2 mils to about 250 mils and having an internal cavity accessiblethrough an opening, the plastic being pliable and the inner layercomponent -being a rigid composition formed within said internal cavityand comprising a filler bonded by the elastomer solids of a latex, saidinner layer being in intimate contact with the inner walls of the outerlayer and engaged with the entire extent thereof and wherein said innerlayer component contains at least about 200 weight parts of iiller foreach weight parts of elastomer solids.

References Cited UNITED STATES PATENTS 2,794,756 6/ 1957 Leverenz.2,959,820 11/1950 Miller et al 264-310 3,071,817 1/1963 La Porte264--302 2,901,377 8/1959 Bode 117--70 FOREIGN PATENTS 218,027 10/ 1958Australia.

ROBERT F. BURNETT, Primary Examiner.

M. A. LITMAN, Assistant Examiner.

